class Solution {
public:
    /**
     * 反转字符串
     * @param str string字符串 
     * @return string字符串
     */
    string solve(string str) {
        int left = 0;
        int right = str.size() - 1;
        while(left < right) {
            swap(str[left], str[right]);

            left++;
            right--;
        }
        return str;
    }
};